So, for anyone who is having a hard time understanding this concept, I was at the same place yesterday. Today I restarted watching it, but before that I went to ChatGPT. It gave me a simple explanation:
Imagine a suitcase (Object) with clothes inside (Data)
Object = the suitcase
Has a baggage tag (name)
Has a position on the airport floor (location)
Can be rotated or scaled
You can move the suitcase around without changing what’s inside
Data = the clothes inside
The actual mesh/geometry, UVs, vertex groups, etc.
If you open the suitcase and change the clothes, you’re editing the data
Linked duplicates (Alt+D)
Imagine making a second suitcase with the same clothes inside.
Move either suitcase anywhere — they move separately.
But if you open one and change the clothes, both now have the new clothes.
(That’s because they share the same data block.)
Real duplicates (Shift+D)
Imagine making a new suitcase with its own copy of the clothes.
Move them independently, and editing the clothes in one won’t affect the other
Then I rewatched the video and … crystal clear! Thank you!